The present invention relates to a method of manufacturing a sintered ceramic body by forming a ceramic powder into a predetermined shape by injection molding and sintering the molded body.
In a conventional method of manufacturing a sintered body made of a ceramic material such as silicon nitride, a sintering accelerator is added to a ceramic powder, and a resultant mixture is sintered in a mold having a cavity of a predetermined shape at a pressure of 150 to 500 kg/cm.sup.2 at a temperature of 1,700.degree. to 1,800.degree. C. This method is called hot pressing. According to this method, a sintered body having a high density and high mechanical strength can be obtained. However, it is difficult to prepare a sintered body of complicated shape by the hot pressing. In addition to this disadvantage, hot pressing is not suitable for mass production.
Recently, a sintering method has received a great deal of attention, since it allows mass production. The sintering method involves adding an organic binder to a mixture of a ceramic powder and a sintering accelerator, and injection-molding the resultant composition. The binder is then removed from the molded body, and the molded body which is free from the binder is sintered. A conventional ceramic powder used for injection molding is obtained by milling a ceramic material in a solvent such as n-butanol to obtain a ceramic powder. The conventional ceramic powder obtained by this wet milling is low in packing density, thus requiring a large amount of binder and a long period of time for removing the binder. In addition, contraction of the material during sintering is great. As a result, a sintered ceramic body having precise dimensions cannot be prepared.